Method of manufacturing composite metal bodies



Jan. 8, 1929., 1,698,300

W. EH LERS METHOD Off MANUFACTURING COMPOSITE METAL BODIES Filed Feb.8.,.1927' I'nv ehtQT: Walther" Ehl'er's,

His Attorney Patented Jan. 8, 1 929.

UNITED STATES PATENT ori ice.

WALTHER EHLEBS, or 'corENIcx-BEnLm. GERMANY, ASSIGNOR TO GENERALfELEczrrarc COMPANY, A conrormrron 0F-NEW YORK.

METHOD OF MANUFACTUQRING COMPOSITE METAL BODIES.

Application filed February 8, 1927, Serial No. 166,802,,ai1d in GermanyJuly 15, 1926.

My invention relates to the manufacture of bodies of compressedparticles of electrically conductive or magnetic material,

press employed, the different speeds use for compressing the timeconsumed with the pressing operation, and the degree of skill of theworkman.

The object of my invention is to provide a method of conducting thepressing operation whereby the properties of the compressed articleswill be independent to a large extent of the variations in the processesof pressing which are employed.

My invention depends upon the discovery of the fact that a point ofsubstantially constant density exists when pulverized material ispressed; that is, when the pressing operation is carried to a certainpoint the density of the compressed body will be substantially constantover quite a wide range in the pressure employed. For example, if apowder in a mold is'gradually 'pressed with a hydraulic press beginningwith zero pressure, the density of the pressedbody first increasesrapidly with increasing pressure, it then increases more slowly, andfinally remains constant up to a certain pressure. The increase of thedensity or the decrease of volume is caused in this instance by theshifting of the individualparticles with respect to one another. Untilthe minimum of volume is reached,-the increase of the pressure will notcause any appreciable increase in the density.

In the accompan ing drawing, I have indicated a curve s owing therelation between density and pressure, the density being'represented bythe ordinates and the pressure b abscissae It will e seen from thiscurve that the density of the body gradually increases with increase ofpressure until a pressure corresponding to P; is reached; The densitythen remains substantially constant over the range K until the pressurecorresponding to P is reached. If beyond this pointthe pressure isincreased to very high values the density of the body increases andapproaches asymptotically the density S,., which represents the densityof the particles of whichthe body is composed.

If in the case illustrated, a pressure corresponding to P is chosen asthe pressure,

7 will be. suflicient.

Attempts have been made in the past to manufacture pressed bodies withuniform characteristics which would be little dependent on the variationof pressure by choosing a range of pressure at a point where the DPapproaches asymptotically the limiting value S... This process, however,requires the application of exceptionally high pressures whlch should beavoided as far as possible in view of the technical difliculties ofproducing such high pressures, such for example, as producing molds ofsufficient strength. It-will also be' found frequently that thecharacteristics of the compressed body are less desirable due to thegreatdeformation of the powdered particles. Moreover, in.- this part ofthe curve the density only is comparatively independent of the pressure,while the magnetic and electrical properties of the compressed body arenot independent of the pressure. What Iv laim as new and desire tosecure by Letters Patentf'of the United States, is:'

constructing bodies of pressed powdered. material which consists inapplying to a mass of powdered material a pressure ofa value within arange over which the density is substantially independa pressure of avalue within a range over ent of the pressure, and below pressures atwhich appreciable difierences of pressure which a further increase indensity will be produce no appreciable. change in the elec- 0 produced.trical and magnetic properties of the body.

5 3. The method of constructing bodies of In Witness whereof, I havehereunto set pressed magnetic material which consists in my hand this17th day of January 1927. applying to a mass of powdered materialWALTHER EHLERS.

